1. Field of the Invention
This invention relates to methods for recycling floor coverings, such as carpet or carpet tile, and in particular, for recycling carpet or carpet tile having a backing, precoat, or adhesive layer containing polyurethanes.
2. Description of the Related Art
Polyurethane resins, which are the reaction products of polyisocyanates and polyols, can be used in a variety of different applications, including in the backing, precoat, or adhesive layers of carpet and carpet tiles. However, the use of virgin polyurethane requires the use and handling of significant quantities of polyisocyanates (as used herein, the term “polyisocyanate” includes diisocyanates, as well as isocyanates having more than two isocyanate moieties), which can cause health and safety problems, and require a high degree of care in handling and disposal. In order to reduce the reliance on virgin polyurethane, and the need for handling of, and exposure to, polyisocyaziates, it would be desirable to reuse polyurethanes in existing carpets and carpet tiles.
Traditional approaches to recycling and reuse have involved separating the individual components to be reused or making do with mixtures of components, which often render the recycled materials suitable for only uses in products of a quality lower than that of the recycled product. Separating individual components of multilayered products, while often more feasible than separating more homogeneous mixtures, can nevertheless present significant difficulties where the layers are held together with adhesive. Often, the separation processes render one or more of the components unusable, or usable only after significant additional processing. For example, processes that involve heating polyurethanes to very high temperatures can often result in irreversible degradation of the polyurethane molecule, in effect “downgrading” it by rendering it unsuitable for recycle or reuse in applications where it will have an equivalent value to virgin polyurethane.